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89 E150 302 AOD - surging idle and low power #740361
September 14th 2018 11:56 am
September 14th 2018 11:56 am
Joined: Jul 2018
Posts: 75
Raleigh, NC
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bubbafat Offline OP
journeyman
bubbafat  Offline OP
journeyman
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Joined: Jul 2018
Posts: 75
Raleigh, NC
When I idle, I can feel a periodic surge especially for the first minute. I also can get a little surge when rolling forward slowly. I don't have a tach but I'd guess it's going up a few hundred rpm.

Along with this, on relatively flat roads I have no trouble getting to 65+ and cruising. But going up even moderate hills, I lose power and am putting the pedal down.

My inclination is to do the following in this order:

- air filter
- red line fuel additive to clean up the throttle body and injectors
- look for vacuum leaks
- MAF replacement
- IAC replacement

How can I be more methodical about this? I'm willing to buy/rent tools but I will be doing this solo and am just learning so want to stay in my wheelhouse. I'm willing to pay a mechanic as needed but want to start on my own.

Suggestions?

Last edited by bubbafat; September 14th 2018 12:18 pm.
Re: 89 E150 302 AOD - surging idle and low power [Re: bubbafat] #740362
September 14th 2018 12:35 pm
September 14th 2018 12:35 pm
Joined: Aug 2001
Posts: 11,783
Fircrest, WA
Reed Offline
Maniac
Reed  Offline
Maniac
Joined: Aug 2001
Posts: 11,783
Fircrest, WA
I also have an 89 E150 that was built with a 302/AOD combination. It now has a 351/C-6 drivetrain, but I had the same problems of lack of power and hunting for the right idle speed that you do.

The best tool you can get is a factory service manual. However, by 1989 the systems on vehicles were so the factory service manual is a milti-volume set that can get expensive to buy, even used.

If you cannot find a factory service manual, this website will be your best friend:

http://www.fuelinjectedford.com

Pay close attention to the pages about running a self-test and the two and thgree digit test codes.

Here is my recommendation.

(1) check the throttle position sensor. If you can, try to check it without removing the throttle body. Make sure it has a smooth change in voltage as you work the throttle.

(2) your van has a MAP sensor, not a MAF sensor. The batch fired injection used in Ford trucks and vans of that era was based on MAP, not MAF. The Mustangs got the sequential maf-based fuel injection. But do replace the MAP.

(3) do check for vacuum leaks. You should get a vacuum gauge and have about 18-20 inches of vacuum at idle.

No fuel passes through the throttle body, so fuel additive will not clean it. Fuel additive might clean the injectors, but I doubt it. Fuel is a solvent. Fuel passes at high presure through the injectors the entire time the engine is running. There isn't much of a chance for buildup to form on the nozzles. The electromechanical parts can wear out, so maybe a new set of injectors is in order.

Also check the condition of the timing chain (is the timing steady or does it fluctuate?) and make sure your base timing is set properly to 10 degrees BTDC (remove the SPOUT when you set it. Don't know what the SPOUT is? Check out that website I linked to).

The idle should be silky smooth and not surge like you are experiencing. I went crazy fixing lots of little things before I got my old 302 to idle right. However, I ended up replacing the 302 because it was just plain worn out. A van is a big heavy vehicle and the previous owner of my van used it to haul a 30 foot travel trailer around the country.



Windows- they're what make a van worth owning!
Re: 89 E150 302 AOD - surging idle and low power [Re: Reed] #740364
September 14th 2018 3:35 pm
September 14th 2018 3:35 pm
Joined: Jul 2018
Posts: 75
Raleigh, NC
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bubbafat Offline OP
journeyman
bubbafat  Offline OP
journeyman
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Joined: Jul 2018
Posts: 75
Raleigh, NC
Originally Posted by Reed

The best tool you can get is a factory service manual. However, by 1989 the systems on vehicles were so the factory service manual is a milti-volume set that can get expensive to buy, even used.


I was able to get the factory manual CD so I have everything in PDF form. Maybe I'm just really bad at digging through 4500 pages of information, but I was hoping to find a diagnosis guide for idle conditions like I found for everything else. Hopefully it just a matter of finding it.

Originally Posted by Reed

If you cannot find a factory service manual, this website will be your best friend:

http://www.fuelinjectedford.com


Even with the manuals, that seems like a really good site - thanks.

Originally Posted by Reed

(1) check the throttle position sensor. If you can, try to check it without removing the throttle body. Make sure it has a smooth change in voltage as you work the throttle.


It sounds like the process for this is to:

1. Make sure reference is good (5V)
2. Make sure ground is good
3. While adjusting the throttle, make sure the signal wire goes smoothly between ~1V and 5V?

With the specifics being to back-probe the respective wires with the TPS still hooked up.

The videos I've watched of people doing this have all had a throttle cable - it's not clear to me from the service manual if my engine is drive-by-wire or has a mechanical connection between the pedal and throttle body. I'm sure I can figure this out by looking once it stops raining.


Originally Posted by Reed

(2) your van has a MAP sensor, not a MAF sensor. The batch fired injection used in Ford trucks and vans of that era was based on MAP, not MAF. The Mustangs got the sequential maf-based fuel injection. But do replace the MAP.


As soon as I locate it - I believe it's near the AC/heater housing inside the engine compartment?

Originally Posted by Reed

(3) do check for vacuum leaks. You should get a vacuum gauge and have about 18-20 inches of vacuum at idle.


Will be doing this.

Originally Posted by Reed

No fuel passes through the throttle body, so fuel additive will not clean it. Fuel additive might clean the injectors, but I doubt it. Fuel is a solvent. Fuel passes at high presure through the injectors the entire time the engine is running. There isn't much of a chance for buildup to form on the nozzles. The electromechanical parts can wear out, so maybe a new set of injectors is in order.


Could be - I was hoping to avoid this at least for a while.

Originally Posted by Reed

Also check the condition of the timing chain (is the timing steady or does it fluctuate?) and make sure your base timing is set properly to 10 degrees BTDC (remove the SPOUT when you set it. Don't know what the SPOUT is? Check out that website I linked to).


I had the timing chain checked (but not the timing) when I had the water pump replaced a month ago. It was in good shape. I gave them the go-ahead to change it if needed and they said it was not needed. They did replace the cover with the pump, though.

Originally Posted by Reed

The idle should be silky smooth and not surge like you are experiencing. I went crazy fixing lots of little things before I got my old 302 to idle right. However, I ended up replacing the 302 because it was just plain worn out. A van is a big heavy vehicle and the previous owner of my van used it to haul a 30 foot travel trailer around the country.


Thankfully this van doesn't have a hitch and has never towed anything. But that doesn't mean the engine was well cared for. I have no reliable information from the previous owner.

Thank you very much for the info - I'll start digging into this.


Re: 89 E150 302 AOD - surging idle and low power [Re: bubbafat] #740366
September 14th 2018 3:47 pm
September 14th 2018 3:47 pm
Joined: Aug 2001
Posts: 11,783
Fircrest, WA
Reed Offline
Maniac
Reed  Offline
Maniac
Joined: Aug 2001
Posts: 11,783
Fircrest, WA
It sounds like you have the process for checking the TPS in hand.

Your van has a throttle cable from the pedal to the throttle body. It is not a computer controlled throttle body (aka drive by wire).

Yes- the MAP is mounted up above the heater/AC box in the engine bay It is directly above and to the rear of the battery. I went through several until i got a good one from Autozone. Take my advice- don't buy cheap discount parts. Save money and frustration in the long run and buy the more expensive good quality name brand parts.

Good luck!


Windows- they're what make a van worth owning!
Re: 89 E150 302 AOD - surging idle and low power [Re: Reed] #740371
September 14th 2018 4:09 pm
September 14th 2018 4:09 pm
Joined: Jul 2018
Posts: 75
Raleigh, NC
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bubbafat Offline OP
journeyman
bubbafat  Offline OP
journeyman
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Joined: Jul 2018
Posts: 75
Raleigh, NC
Originally Posted by Reed
Take my advice- don't buy cheap discount parts. Save money and frustration in the long run and buy the more expensive good quality name brand parts.


I'll stick with Motorcraft for things we've talked about here. I should probably care more about money, but $20 here or there is nothing compared to having it work the first time.


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